In industrial gas analysis, extractive gas detection and analysis begins with the collection of gas to be analyzed. This often involves bringing the gas from a hostile environment, such as the inside of a smoke stack, to equipment capable of performing an analysis of the gas, which is usually not in the same environment (i.e., the gas detection equipment is outside the smokestack). The gas is carried through tubing, usually ¼″-stainless steel or plastic. Gas temperature differences between where the gas is sampled (typically >100 degrees Celsius), and where the analysis equipment is located (room or outside temperature) can cause critical components of the sampled gas to condense inside the tubing before reaching the detection equipment. For this reason, the tubing is often heated the entire distance between the sampling point and the detection equipment. Another solution is to introduce a dilution gas into the tubing, along with the sampled gas stream, to prevent condensation of key components of the gas even though the temperature decreases as the gas travels through the tubing. The dilution gas is chosen such that it does not interfere with the detection equipment or the compounds sought to detect, and it often consists of dry air or nitrogen. It is mixed at ratios ranging from twenty to four hundred parts dilution gas to one part sampled gas.
The detection equipment that is employed depends on the application, but often consists of several separate units; each unit detects one compound or one family of compounds. One common detector determines the quantity of nitric oxide (NO) by measuring the intensity of light that is emitted when ozone (O3) is reacted with NO. This common technique is referred to as chemiluminescence and has been the main-stream industry measurement standard for NO concentration since the 1960's. Other pieces of equipment can detect sulfur dioxide (SO2), carbon dioxide (CO2), carbon monoxide (CO), mercury (Hg), and the NO detector can also be configured to detect nitrogen dioxide (NO2).
Other detector technologies using atomic emission techniques have limitations on use, such as Atomic Emission Detectors (AED). These instruments typically sample gas, and then introduce the gas into an inductively coupled plasma (ICP) at low pressure. The instrument is generally limited to bench-top laboratory applications due to its size and power requirements, and it has the complexity of transporting the sampled gas from the source to the low-pressure plasma region. Mass spectrometers (MS) involve a complicated sampling technique to first ionize the sampled gas and then introduce it into a low-pressure analysis chamber. These systems suffer from size and power requirements making economic compact analyzers out of reach.
Still other detection approaches try to measure the gas in the stack environment without transporting it to the equipment. One of these approaches is Laser Induced Breakdown Spectroscopy (LIBS), which needs a relatively expensive laser system for operation. Spectroscopic detector technologies such as fourier transform infrared spectroscopy (FTIR) have size and costs restrictions, and FTIR cannot detect atomic species nor homonuclear species such as Hg, Cd, Se, Cu, Zn, Pb, Ni, O2, N2, Cl2, etc.
Thus a need has long existed for a Axial-Geometry Micro-Discharge Detector that would do all of the following:                1. Be capable of simultaneously detecting a wide variety of molecules and atoms.        2. Be capable of operating on battery power.        3. Be capable of operating in hot and toxic environments.        4. Eliminate the need for sampling lines.        5. Be economical and compact.        6. Not require excessive supporting equipment.        7. Allow adaptation with gas chromatograph equipment.        